PSMA-PET in Men With Nonmetastatic Castration-Resistant Prostate Cancer

[Balsam01]

TAKE-HOME MESSAGE

•In this study, the authors retrospectively assessed 200 patients with castration-resistant prostate cancer (nm-CRPC) using the same inclusion criteria as in the PROSPER, SPARTAN, and ARAMIS phase III trials, including no evidence of metastatic disease per conventional CT and bone scans. Using PSMA-PET, disease was detected in 196 of 200 patients. Overall, pelvic disease was detected in 44%, including 24% with local prostate bed recurrence; and M1 disease was detected in 55%, despite negative findings using conventional imaging.

•This is a very important clinical study, as the results suggest that the nmCRPC space may be a virtual space that will tend to disappear with the increased use of PET scans in the near future.

– Pedro C. Barata, MD

PURPOSE

Systemic androgen-signaling inhibition added to ongoing androgen-deprivation therapy (ADT) improved clinical outcomes in patients with nonmetastatic castration-resistant prostate cancer without detectable metastases by conventional imaging (nmCRPC). Prostate-specific membrane antigen ligand positron emission tomography (PSMA-PET) detects prostate cancer with superior sensitivity to conventional imaging, but its performance in nmCRPC remains largely unknown. We characterized cancer burden in high-risk patients with nmCRPC using PSMA-PET.

EXPERIMENTAL DESIGN

We retrospectively included 200 patients with nmCRPC, prostate-specific antigen (PSA) >2 ng/mL, and high risk for metastatic disease [PSA doubling time (PSADT) of ≤10 months and/or Gleason score of ≥8] from six high-volume PET centers. We centrally reviewed PSMA-PET detection rate for pelvic disease and distant metastases (M1). We further evaluated SPARTAN patients stratified by risk factors for PSMA-PET-detected M1 disease.

RESULTS

PSMA-PET was positive in 196 of 200 patients. Overall, 44% had pelvic diseases, including 24% with local prostate bed recurrence, and 55% had M1 disease despite negative conventional imaging. Interobserver agreement was very high (κ: 0.81-0.91). PSA ≥ 5.5 ng/mL, locoregional nodal involvement determined by pathology (pN1), prior primary radiation, and prior salvage radiotherapy independently predicted M1 disease (all P < 0.05).

CONCLUSIONS

PSMA-PET detected any disease in nearly all patients and M1 disease in 55% of patients previously diagnosed with nmCRPC, including subgroups with PSADT of ≤10 months and Gleason score of ≥8. The value of PSMA-PET imaging for treatment guidance should be tested in future studies.

Article Citation: Clinical Cancer Research

Prostate-Specific Membrane Antigen Ligand Positron Emission Tomography in Men With Nonmetastatic Castration-Resistant Prostate Cancer

Clin. Cancer Res 2019 Dec 15;25(24)7448-7454, WP Fendler, M Weber, A Iravani, MS Hofman, J Calais, J Czernin, H Ilhan, F Saad, EJ Small, MR Smith, PM Perez, TA Hope, I Rauscher, A Londhe, A Lopez-Gitlitz, S Cheng, T Maurer, K Herrmann, M Eiber, B Hadaschik